| This dissertation combining with practical project, studies the critical technology of the NIBASHAN deep buried and extra-long tunnel of Bei Jing-Kun Ming highway. The key rock mass engineering problem along tunnel, which is the key and bottleneck project of Ya'an to Lu Gu, were researched according to the field sketch, experiment both in laboratory and field, simulative calculation and theoretical analysis. By more than three years'study, some progress and conclusion were given as follows:(1) On the basis of collecting and analyzing exsting basic geological data and filed geological work, it is included that:The Daxiangling articline is not overturned,but similar to the outline of "box";there is a varied topography, numerous stratum and complex spatial distrbution, the modern tectonics stress is high, complex formation condition; The rock mass structure is complex because of the tectonic influence in tunnel area; well-developed fold and faults which is exert an influence to geostress.Tectonic damage in NIBASHAN tunnel area is obviously distributed in belt, including strong tectonic damage zone, medium tectonic damage zone and weak tectonic damage zone.(2) A series of rock mechanics experiments were carried include uniaxial compression test, uniaxial tensile test, triaxial compression and unloading tests.the following results have been drawn:Integral rock with high compressive strength, the max compressive strength is about 250MPa, Microcracks cast influence on the compressive strength,and the strength is about 20MPa if microcracks are well developed,the average is between 70MPa to 100MPa. With the increase of buried depth, the peak strength become higher; Loading paths influence on the triaxial compressive strength and deformation.(3) To get the geostress, Hydraulic fracturing method, focal mechanism solution and Kaiser effect were used. Results as follows:The geostress increase with the depth of burial, the max principal stress is between 40MPa to 45MPa; the vertical stress less than horizontal stress,when the depth lower 300m,the vertial stess lies in bwtween the min principal and the max principal stress if the depth ranges from 300m to 850m,the vertical stress more than horizontal stress,when the depth greater 850m; The direction of max principal stress in tunnel area is N55°W, it is intersect trend of tunnel with large angle.(4) Based on the site test results,numerical calculation shows that:Topography have an obvious effect on geostress, the grostress of import and exit is low, tunnel of middle is larger; The maximum principal stress in deep-buried tunnel is between 30MPa to 45MPa, the intermediate principal stress is between 20Mpa to 30MPa, the min. principal stress is between 10Mpa to 20MPa.(5) Based on the site tests and the rock tests, numerical simulation and theoretical analysis were carried to predict the fatalness of rockburst. Analysis by energy theory and theory of strength showns that:the length that rockburst may occur in Nibashan tunnel is 29% of total tunnel, including:weak rockburst tunnel is about 20%, medium rockburst tunnel is about 7%, serious rockburst is about 2%. Because of fault zone and difference of rock joint, the tunnel that rockburst may occur is un-continuous, and belt-distributed along the tunnel.(6) Large deformation is defined as non-brittle failure, the deformation exceed the reserved deformation, when the relative deformation of the side is more than 0.013(Db≥0.013),it is intitule large deformation. This essay separately calculates out the variables of each section in tunnel through rock mechanical theory and FLAC3D. The results shows that:the sections with serious large deformation are all with high in-suit stress and in fault zone of surrounding rock, three is serious large deformation in individual sections; Engineering characteristic and texture characteristics of rock mass in fault zone influence large deformation, there be obvious large deformation, when the width of fault zone is over 19m.
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